The present invention relates to a method and apparatus for studying and screening agents useful for regulating the growth of biological material and the deposition of organic and inorganic contaminants on coupons. More particularly, the present invention is directed to a method and apparatus for studying and screening biocidal agents useful in regulating the growth of bacteria on stainless steel coupons.
Many industrial processes, such as pulp and paper making, utilize water and/or other liquid material in processing steps. Such process liquid typically provides an excellent supply of carbon and nutrients which promote bacterial growth. In paper mills, for instance, bacterial films (xe2x80x9cbiofilmsxe2x80x9d) undesirably and readily form on the steel surfaces of process equipment used during manufacture. Such biofilms typically are accompanied by protective exopolysaccharides (xe2x80x9cslimexe2x80x9d) and occur at the interface of these equipment surfaces and process water streams. Additionally, inorganic contaminants, such as calcium carbonate (xe2x80x9cscalexe2x80x9d) and organic contaminants often deposit on such surfaces. These organic contaminants are typically known as pitch (e.g., resins from wood) and stickies (e.g., glues, adhesives, tape, and wax particles).
The growth of biofilm and the deposition of these inorganic and organic contaminants can be detrimental to the efficiency of such equipment causing both reduced product quality, reduced operating efficiency, and general operational difficulties in the systems. Biofilm growth and organic and inorganic contaminant deposition on consistency regulators and other instrument probes can render these components useless, and such growth and deposition on screens can reduce throughput and upset operation of the system. Growth and deposition can occur not only on metal surfaces in the system, but also on plastic and synthetic surfaces such as machine wires, felts, foils, Uhle boxes and headbox components. The difficulties posed by these growths and deposits include direct interference with the efficiency of the contaminated surface, resulting in reduced production, as well as holes, dirt, and other sheet defects that reduce the quality and usefulness of the paper for operations that follow like coating, converting or printing.
Consequently, methods of preventing and removing the build-up of such growths and deposits on pulp and paper mill equipment surfaces are of great industrial importance. While paper machines can be shut down for cleaning, this is undesirable as it necessarily results in a loss of productivity and the product which results prior to such cleaning is of poor quality as it is partially contaminated from growths and deposits which break off and become incorporated into product sheets. Likewise, removing growths and deposits also necessarily results in the formation of poor quality product which is manufactured prior to such removal. Preventing biofilm growth and contaminant deposition is thus greatly preferred as it allows for consistently high quality product to be produced in an efficient manner. Particularly, the use of compositions comprising gelatin, such as those described in U.S. Pat. No. 5,536,363 to Nguyen, have been found to be well suited for regulating the deposition of organic and inorganic contaminants in pulp and papermaking systems.
The growth of slime on metal surfaces creates an environment which is conducive to corrosion. This microbially-influenced corrosion typically occurs at the interface between the slime and the metal surface. Also, fouling or plugging by slime readily occurs in pulp and paper mill systems. Typically, the slime becomes entrained in the paper produced and causes breakouts on the paper machines with consequent work stoppages and the loss of production time. It also causes unsightly blemishes in the final product, resulting in rejects and wasted output. These contamination problems have resulted in the extensive utilization of biocides in water used in pulp and paper mill systems. Agents which have enjoyed widespread use in such applications include chlorine, organo-mercurials, chlorinated phenols, organo-bromines, and various organo-sulfur compounds, all of which are generally useful as biocides but each of which is attended by a variety of impediments.
Known means of studying biological material typically involve the flow of an aqueous sample containing the biological material over a solid support, such as with a flow through cell assembly. Typically, a pressure means, such as an inert gas, and/or a vacuum means are used to cause the sample to contact the solid support. For example, U.S. Pat. No. 5,641,458 to Shockley, Jr. et al. discloses a flow through cell device for the non-invasive monitoring of bodily fluids. The device includes sensors which interact with a fluid sample through a semi-permeable membrane. Sensors attached to the membrane allow for photochemical reactions involving the fluid sample to be monitored optically.
U.S. Pat. No. 5,624,815 to Grant et al. discloses a method and apparatus for analyzing biological material by passing a liquid sample through a number of discrete wells which are adapted to retain the biological material. The liquid sample is drawn into the wells through a vacuum mechanism. Also, U.S. Pat. No. 5,792,430 to Hamper, U.S. Pat. No. 5,624,815 to Grant et al., U.S. Pat. No. 4,908,319 to Smyczek et al., and U.S. Pat. No. 4,753,775 to Ebersole et al., all disclose means for studying biological material in which a liquid sample is drawn over a solid support.
As conditions such as temperature, pH, and the presence of organic and inorganic materials can vary greatly among and within manufacturing processes, there is a continuing need to investigate materials useful for the prevention and removal of biofilms and organic and inorganic contaminants that form on process equipment functioning under these various conditions. Known experimental techniques, such as those described above, are not well suited for such investigations. While they are suited for the specific investigation of certain biological material, they do not allow for an efficient and thorough analysis of the effect of numerous and various chemicals and compositions on a variety of substrates under select conditions.
Additionally, it is known to monitor biofilm growth in water systems, such as through the apparatuses and methods described in U.S. Pat. No. 5,049,492 to Sauer et al. and U.S. Pat. No. 6,017,459 to Zeiher et al., to allow for the sampling of water during manufacturing processes. While these apparatuses and methods are important in determining, and consequently maintaining, the quality of the water stream, of greater importance is the discovery and development of compositions which will prevent and/or destroy the growth of biofilms and inorganic and organic contaminants in the water stream. Therefore, there exists a need for a model experimental system and a method involving such a system by which the efficient investigation of substances useful in regulating the growth of biological materials and the deposition of inorganic and organic contaminants on equipment surfaces such as those used in pulp and papermaking processes may be conducted.
In one aspect, the present invention provides a device for permitting fluid flow, such as whitewater or synthetic whitewater endemic to pulp and papermaking systems, over a coupon. The device includes a tray body (tray) which defines a coupon receiving chamber, a fluid inlet passageway in fluid communication with the coupon receiving chamber, and a fluid outlet passageway in fluid communication with the coupon receiving chamber. The tray body provides for fluid to enter the fluid inlet passageway, contact the coupon, and enter the fluid outlet passageway.
Preferably, the tray body is a substantially elongate member including first and second opposed side surfaces, first and second opposed major surfaces, with the coupon receiving chamber accessible through the first major surface. The tray body may include a plurality of coupon receiving chambers which are adapted to receive substantially elongate stainless steel coupons.
The coupon receiving chamber is in partial overlying registry with the fluid inlet passageway and the fluid outlet passageway and includes a coupon support surface and an upstanding perimetrical wall bounding the coupon support surface. The coupon support surface further defines a fluid inlet port in fluid communication with the fluid inlet passageway and further defines a fluid outlet port in fluid communication with the fluid outlet passageway. The tray body further defines a fluid inlet aperture which is opposite the fluid inlet port and which is in fluid communication with the fluid inlet passageway.
The tray body accommodates a fluid feed conduit for delivering a fluid through the fluid inlet aperture and further defines a fluid outlet aperture which is opposite the fluid outlet port and which is in fluid communication with the fluid outlet passageway. Further, the tray body accommodates a fluid discharge conduit for conducting fluid through the fluid outlet aperture.
In a preferred embodiment of the present invention, the coupon support surface is elongate and the fluid inlet and fluid outlet ports are defined at opposite ends of the coupon support surface. The present invention may also include a cover which is in removable sealing registry over the coupon receiving chamber. Additionally, the present invention may also include a gasket supported between the tray body and the cover for further sealing the coupon receiving chamber.
In a method aspect of the present invention, a method is provided for studying and screening agents useful for regulating the growth of biofilm and the deposition of organic and inorganic contaminants on a coupon surface which includes the steps of: (i) providing a device which regulates fluid flow over the coupon surface, wherein the device includes a tray body defining a coupon receiving chamber, a fluid inlet passageway in fluid communication with the coupon receiving chamber and a fluid outlet passageway in fluid communication with the coupon receiving chamber; (ii) placing the coupon in the coupon receiving chamber; and (iii) effecting a fluid flow over the coupon. The present invention may also include the step of determining the growth of biological material on the coupon, such as by subjecting the coupon to staining and microscopy.
The present invention may further include the step of directing the fluid flow through the fluid inlet passageway and directing the fluid flow to the fluid inlet passageway by a fluid feed conduit. Further, the present invention may include the step of directing the fluid flow across the coupon, through the fluid outlet passageway, and from the fluid outlet passageway through a fluid discharge conduit.